Flying beneath the radar: New Zealand’s ‘minor’ wild ungulates
For a country that prehistorically had no native land mammals other than bats, New Zealand is now home to a surprising variety of ungulates. If moose are not yet extinct, and with wapiti now classed as separate from red deer, there are 15 species of ungulate (including local feral populations of ‘domestic’ sheep, cattle and horses) that still have one or more viable wild population.
Most New Zealanders are aware that there are widespread populations of feral goats, pigs and red deer, which provide a substantial hunting resource. These often have significant unwanted impacts on agriculture and the native environment, and there have long been efforts to reduce their numbers (as in the deer culling era of the 1930–1950s). Other species, such as Himalayan tahr, are less widespread and less well known but are intensively controlled in some places, particularly to prevent them spreading to new areas. These thus feature prominently on the radar screens of wildlife management agencies.
In contrast, tucked away in the backblocks of the Bay of Plenty and Manawatū are comparatively small populations of sambar deer. Nestled at the head of Lake Wakatipu in Otago is a small herd of white-tailed deer, with a second herd on Stewart Island. However, having small geographic ranges does not mean these animals cause negligible damage to the environment. The damage can be significant, even if localised. Yet these minor species often go unmanaged. This may be a deliberate management decision because their impacts fall below a priority threshold when budgets are limited, or because there is inadequate information about their numbers, distribution and damage. In either case, they often tend to drop off the wildlife management radar, notwithstanding the advocacy of the newly formed NZ Game Animal Council (GAC).
Here we examine some of these ‘minor’ ungulate species in the light of three topical issues. First, there is evidence that some have expanded their ranges and become more abundant. This could increase their impacts on native biodiversity. Second, some are important game animals and their populations may qualify as ‘herds-of-special-interest’ (HoSI) as proposed by the GAC. Third, some geographically isolated herds may provide excellent case studies for eradication, with potentially important lessons for initiatives such as Predator Free NZ, despite their being herbivores.
With regards to native biodiversity, the impact of minor browsing species on vegetation is certain to differ to some degree from that of the more common species. They obviously also have far greater potential to spread to new areas, adding to the overall conservation threat. A good example of this is fallow deer. In the late 1990s, Wayne Fraser and colleagues identified 42 new populations of fallow deer in New Zealand, equating to 16% of all new populations of wild ungulates. Observations suggest that many of these have since established and expanded. Further new populations have also emerged, almost exclusively due to farm escapes and illegal liberations (a pattern that holds for nearly all wild ungulates). While those responsible for such liberations, and some affected landowners and hunters, may be delighted with additional herds and the hunting opportunities they provide, other landowners, conservation groups, the Department of Conservation and regional councils may not be so happy.
Eradication of the new populations of fallow deer is probably achievable because they currently occur at low numbers and have low annual rates of dispersal. However, once neighbouring herds begin to expand into adjacent suitable habitat and merge with one another, it is probable that future attempts at eradication will be more difficult, because it will be difficult to find and kill them all. This will lead to recolonisation of controlled areas by adjacent uncontrolled herds. It is also likely to result in an inability to kill deer in the population faster than their rate of increase. These factors will increase both the cost of any eradication attempt and its social complexity (i.e. getting buy-in from a larger number of affected landowners).
Chamois are another ‘minor’ species that warrant further attention. Their impacts on native vegetation remain poorly documented, but also likely to be large at high numbers and different from those of other ungulates. Tahr often outcompete chamois, so their management may have unintended consequences for biodiversity via chamois population dynamics and ecology. Quantitative data are needed to ascertain if the damage caused by these and other minor ungulate species is sufficiently high to warrant management intervention.
Although the minor ungulates are usually not front-and-centre on the conservation radar, they have long been a priority when it comes to management for hunting; they are perceived as ‘special’ simply because they are less common. However some, such as fallow deer, sika deer and white-tailed deer, have tended to occur at higher densities than red deer since the 1970s due to their being smaller and therefore less important for commercial hunters. Such species thus have high representation among the original 10 Recreational Hunting Areas formally established in the early 1980s. Wapiti, sika deer, white-tailed deer and fallow deer are under active consideration by the GAC for the same reasons, as it looks to establish and manage more HoSI.
A working example of the complexities in managing HoSI is the Fiordland wapiti herd, which is actively managed for hunting benefits under an agreement with DOC. The organisation that manages the herd, the Fiordland Wapiti Foundation, is funded by donations from recreational hunters, and uses that money to subsidise commercial deer culling aimed at reducing the proportion of red deer, red deer–wapiti hybrids, and female wapiti in the area. This keeps overall deer numbers and their impacts on the native vegetation at acceptable levels. Such management increases hunters’ chances of getting a highly sought-after trophy wapiti, without worsening overall conservation outcomes. The fundamental goal of delivering benefits within overriding environmental considerations will apply to all HoSI.
Although simple in principle, achieving game management within acceptable environmental limits will require far more information about the biology, ecology and conservation impacts of these minor herds than is currently available. It is likely that some of these minor herds will become key ‘laboratories’ in helping unravel the complexities of the hunter–animal–impact relationships.
This work was funded by Manaaki Whenua − Landcare Research Strategic Science Investment Funding.
A. David M. Latham